1. Field of the Invention
The present invention relates generally to the field of inhalation devices, and more specifically, to inhalation devices that utilize acoustic control to facilitate breath activation of different systems of the inhalation device. Particular utility for the present invention is found in the area of facilitating inhalation of powdered medications.
2. Brief Description of Related Prior Art
Certain diseases of the respiratory tract are known to respond to treatment by the direct application of therapeutic agents. As these agents are most readily available in dry powdered form, their application is most conveniently accomplished by inhaling the powdered material through the nose or mouth. Alternatively, the drug in this form may be used for treatment of diseases other than those of the respiratory system. When the drug is deposited on the very large surface areas of the respiratory tract, it may be very rapidly absorbed into the blood stream; hence, this method of application may take the place of administration by injection, tablet, or other conventional means.
Several inhalation devices useful for dispensing this powder form of medicament are known in the prior art. For example, in U.S. Pat. Nos. 3,507,277; 3,518,992; 3,635,219; 3,795,244; and 3,807,400, inhalation devices are disclosed having means for piercing of a capsule containing a powdered medicament, which upon inhalation is drawn out of the pierced capsule and into the user's mouth and thus, into the user's lungs and respiratory system. Several of these patents disclose propeller means, which upon inhalation aid in dispensing the powder out of the capsule, so that it is not necessary to rely solely on the inhaled air to suction powder from the capsule. For example, in U.S. Pat. No. 2,517,482, issued to Hall, a device is disclosed having a powder containing capsule which is pierced by manual depression of a piercing pin by the user. U.S. Pat. No. 3,831,606 discloses an inhalation device having multiple piercing pins, propeller means, and a self-contained power source for operating the propeller means via external manual manipulation, so that upon inhalation the propeller means aids in dispensing the powder into the stream of inhaled air. See also U.S. Pat. No. 5,458,135.
These prior art devices present several problems and possesses several disadvantages which are remedied by the inhalation devices of the present invention. For instance, these prior art devices require that the user exert extreme effort in inhalation to effect dispensing or withdrawal of powder from a pierced capsule into the inhaled air stream.
The above description of the prior art is taken largely from U.S. Pat. No. 3,948,264 to Wilke et al, who disclose a device for facilitating inhalation of a powdered medication. A capsule piercing structure is provided, which upon rotation puts one or more holes in the capsule, which contains medication, so that upon vibration of the capsule by an electro-mechanical vibrator, the powdered drug may be released from the capsule. The electromechanical vibrator includes, at its innermost end, a vibrating plunger rod which is connected to a mechanical solenoid buzzer for energizing the rod to vibrate. The buzzer is powered by a high energy electric cell and is activated by an external button switch. Moreover, as noted above, in Wilke et al.'s disclosed device, vibration of the powder is activated by depressing a push button. This can be difficult and painful for some users (e.g., patients suffering from extreme arthritis). Finally, in order to use Wilke et al.'s disclosed inhaler most efficaciously, the user must depress the vibration-actuating push button at precisely the same time that the user begins inhalation. This can also be difficult for some users (e.g., very young patients, patients suffering from neuromuscular disorders, etc.).
The prior art, such as described above, is dominated by inhaler devices that are activated by some mechanical means of activation, e.g., airflow sensors that include: flapper valves, turbine valves, swirl generators, vortex measurement devices, hot wire, direct pressure drop, ultra sonic, Doppler shift measurement, etc.